Sunitinib is chemically described as N-[2-(diethylamino)ethyl]-5-[(Z)-(5-fluoro-1,2-dihydro-2-oxo-3H-indol-3-ylidine)methyl]-2,4-dimethyl-1H-pyrrole-3-carboxamide and is represented by Formula I.

Sunitinib is an oral multi-kinase inhibitor and is useful for the treatment of gastrointestinal stromal tumors and advanced renal cell carcinoma. Sunitinib is commercially available as an L-malate salt, which is described chemically as butanedioic acid, hydroxy-, (2S)-, compound with N-[2-(diethylamino)ethyl]-5-[(Z)-(5-fluoro-1,2-dihydro-2-oxo-3H-indol-3-ylidine)methyl]-2,4-dimethyl-1H-pyrrole-3-carboxamide (1:1).
U.S. Publication Nos. 2003/0069298 and 2007/0191458 describe the preparation of crystal Forms I and II of an L-malic acid salt of sunitinib. According to these publications, crystal Form I of an L-malic acid salt of sunitinib is prepared by a process comprising slurrying a poorly crystalline or crystal Form II of an L-malic acid salt of sunitinib in acetonitrile, and crystal Form II of an L-malic acid salt of sunitinib is prepared by dissolving crystal Form I of an L-malic acid salt of sunitinib in tetrahydrofuran and water and allowing the solvent to evaporate overnight. PCT Publication No. WO 2009/104021 discloses that Form II of sunitinib L-malate is hygroscopic, thermodynamically unstable, and appears to readily convert to Form I.
PCT Publication No. WO 2011/061613 discloses a stable crystalline Form II of an L-malic acid salt of sunitinib and a process for its preparation. The publication further describes that the stable crystalline Form II does not convert to any other form or absorb moisture on storage.